Overview of Stellar Evolution
- Stars shine as a result of nuclear reactions deep in their interior. As a
star's nuclear energy supplies are used up, it evolves toward an end state that
depends on its mass.

Normal Stars & Star Clusters

In this section we focus on the youth and middle age of stars. Chandra and other X-ray telescopes focus on the high-energy action of this drama - the turbulent, multimillion degree outer atmospheres and gale-force outflows of gas from hot, luminous stars.

Collapsed StarsThe stellar end game inevitably produces dense, collapsed stars - white dwarf,
neutron stars, and black holes - where gravity is strong and conditions are often violent. X-ray telescopes are especially suited to explore these objects, so separate sections are devoted to them.

Young Stars and Star Clusters -
Young stars are much brighter in X-rays than middle-aged stars such as the sun. Stars do not form in isolation, but in clusters which can have thousands of members, so most young stars are found in clusters.

Open Clusters vs. Globular Clusters
Clusters of young stars are irregularly shaped and are called open clusters, to distinguish them from globular clusters, spherically shaped clusters of very old stars.

Normal Stars - Normal, middle-aged stars such as our sun have hot, X-ray- emitting outer atmospheres, or coronas. X-ray observations have proven to be a useful tracer for studying how the turbulent heating near the surface of stars depends on the age, rotation and type of the star, and how the flaring activity of stars changes as stars evolve.

Binary Star Systems - The evolution of stars can be changed dramatically if they are in a close binary system. These changes depend on how close the stars are to one another, and how massive the stars are. Some of the strongest X-ray sources in our galaxy are close binary systems containing neutron stars and black holes.